1. Field of the Invention
The present invention relates to an automation technology for handling articles such as assembly workpieces in a factory or other places. More particularly, it relates to an apparatus capable of picking up articles one by one by using an industrial robot (hereinafter referred to as robot) when many articles are placed in a disorderly pile on a table or on a surface of a box or the like.
2. Description of the Prior Art
In an assembly process in a factory, for example, picking up various articles is a basic work element which is indispensable in almost all cases. To automate this work, a robot or a system incorporating a robot and a visual sensor are used.
A problem with the conventional technology is that it is very difficult for the robot to hold and pick up articles one by one when many articles are placed in a disorderly pile.
For example, where many workpieces W1 to W5 (e.g., five bolts) are placed in a disorderly pile on a tray TR as shown in FIG. 1, it is not easy for a robot to pick up individual workpieces, even with the aid of a visual sensor. Picking up articles is especially difficult for a robot when the holding posture of the robot hand requires a certain accuracy, for example, when the axial direction of a bolt in FIG. 1 must be in agreement with the Z-axis direction of the tool coordinate system.
To solve this problem, conventionally, in many cases, the workpieces W1 to W5 are lined up or positioned such that they do not overlap before the robot picks up the workpieces, as shown in FIG. 2. If the visual sensor is used, the accuracy of lining-up or positioning the workpieces W1 to W5 may be reduced, and in some cases, some overlapping of the workpieces is also allowed.
However, to realize the state as shown in FIG. 2 or a similar state, manual work or a largescale automatic lining-up/positioning mechanism is needed, which presents an obstacle to automating the process using a simple system. Also, with either manual work or the use of an automatic mechanism, the process time may be prolonged by lining-up or positioning the workpieces.